Crime and punishment, chimpanzee-style

Chimps won't punish transgressions unless they were the victim.

New research suggests that chimpanzees do not engage in third-party punishment.

It seems like every time scientists ask whether great apes are capable of an advanced cognitive ability, the answer is yes. Chimpanzees, in particular, seem to push the limits of what we think non-human primates are capable of: they plan ahead, they exhibit altruism, and some have incredible memory skills.

Most recently, researchers asked whether chimpanzees exhibit a sophisticated social behavior called “third-party punishment.” This behavior occurs when one individual punishes another individual for a transgression that did not directly harm the punisher. So in a chimp's case, it might involve an individual punishing a fellow group-member for stealing food from a different group member.

The behavior is considered cognitively advanced, as the punisher must not only understand that the transgression was unfair despite not being involved, but must also be willing to incur some cost and no immediate material gain from the punishment. Third-party punishment is seen often in human societies, and is thought to maintain cooperation by making cheating costly. Because chimpanzees live in large, complex social groups, they have evolved incredible social skills, and researchers thought it was possible that they might demonstrate this type of behavior.

During each trial in the experiment, separate but adjacent cages held three chimpanzees: the “thief,” the “victim,” and a third individual, one that had the ability to dole out punishments. The researchers dropped food onto a tray into the victim’s cage, and via a pulley system, the thief could pull this food-laden tray into his own cage. Once the food was stolen from the victim, the third individual had the opportunity to collapse the tray that was now in the thief’s possession, making the food disappear and thereby punishing the thief for his unfair behavior.

As controls, the experimenters also tested scenarios in which the experimenter moved the food to the thief’s cage (rather than the thief stealing it), the experimenter took the food and placed it in an empty cage, and one where the thief could take food without affecting the victim. If the potential punisher collapsed the tray only in situations where the thief took possession of the victim’s food, the study could conclude that third-party punishment does exist in this species.

Somewhat surprisingly, there was no evidence of third-party punishment among the chimpanzees. Given the opportunity, the potential punisher did not collapse the food tray significantly more often when the thief had actually stolen the food from a victim than in the other situations.

There were two possible explanations for these results: either the chimpanzees didn’t understand the scenario, or they simply don’t exhibit third-party punishment. To distinguish between these possibilities, the experimenters also ran second-party punishment trials, where there were only two chimpanzees involved: a thief and a victim capable of punishment. The difference from the previous trials is that here, the potential punisher was also the victim.

In these trials, the chimpanzees were quick to punish the thief by collapsing the food tray (but only if they were socially dominant to the thief). These results suggest that, although chimpanzees understand unfair behavior and retaliate when they are personally affected, they do not engage in punishment when they are merely a bystander. It appears that, for chimpanzees, punishment may function to coerce others into complying, rather than to discourage unfair behavior.

These findings have significant ramifications for how we understand social behavior in our species and others. First, third-party punishment is thought to maintain cooperation in humans by discouraging cheating; however, while chimpanzees are known to cooperate, they don’t appear to engage in this type of punishment. This raises the question of whether human and great ape cooperation are maintained in different ways, Additionally, if third-party punishment isn’t etched into our evolutionary history, how and when did humans acquire our inclination to punish others for transgressions in which we were not involved? For now, these questions remain unanswered.

75 Reader Comments

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

Punishment, I would bet, started as a control mechanism. Some hilltop lordling started interfering in second-party punishments in order to ensure his favorites prospered over those he didn't like. The rest of the hilltop lordlings thought it was a grand idea.

Thousands of years later, we call our hilltop lordlings "politicians", but the mechanism is much the same.

My original field was evolutionary animal behavior. I mention that because it involves my criticism of the experiments. People will exhibit the same behavior in prisons. They will also often exhibit the same behavior in small social settings. After all animals, and people, don't always behave the same in different groupings.

This is work that really needs to be done in the field, with a natural group of animals. Only long term observation will really tell us what they do under these circumstances. We do know that chimps do exhibit altruistic behavior under a number of different situations involving third parties. This experiment seems to ignore those long term findings.

Isn't the conclusion too premature? Just because this experiment did not observe third-party punishment, does not mean that it doesn't exist/occur in nature.

My biggest objection is that not all humans engage in third-party punishment either. In fact, only a minority do- only the leaders (government) typically punish criminals. I think the chimp given the chance to be third-party punisher would most likely do it if it was an alpha male with some stewardship of the victim or at least some interest/friendship/bond with the victim.

Do this experiment with three human strangers, and I'm sure third-party punishment will not be observed either.

We're two million years separated from chimps. I don't think it's appropriate to imply that if chimps don't exhibit a behavior, then that behavior can not be "etched into our evolutionary history".

One of the posters has also raised a good question: How do humans respond to this type of scenario? I know I would be reluctant to interfere in such a dispute if were me and just two others. I suspect humans usually find ways to dilute the cost to the punishing party. Punishments may be meted out by the group, making it hard for the punished party to focus retribution on any individual. Humans, also, might rely on culture to make the punishments faceless: "I'm not the one who decided that this should be the punishment. The punishment is prescribed by <source>", where <source> may be a deity, "the law", tradition, or some other similar culturally-derived source that does not implicate any individual.

It would be interesting to see what would happen if the entire rest of the troup were in the cage as the punisher. Would one of the troup feel safer executing the punishment if the entire troup could see how justified he was (potentially backing him up against future retribution)? My hypothesis would be that the dominant member of the troup would trigger the punishment. Just like a hunter-gatherer tribal leader mediating a dispute in his tribe. (Not that I think that hypothesis has a high likelihood of holding up, it just seems more fun to go into the experiment with that hypothesis than it would be to go in with the hypothesis of "I think nothing will happen differently if the entire troup is present".)

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study.

dont think he missed the point, the surroundings the chimps are placed in seem like they may be unnatural, taking the chimps out of a social context.

need more information, but the whole thing seemed too foreign as to lose context for the chimps. thus them may not be understanding.

No third-party punishments among chimps? Then what they've found is that monkeys are a lot like soft-on-crime liberals. Liberals have little interest in punishing crimes that don't impact them personally. They'd rather spend money on 'root causes,' which are invariably liberal causes.

That doesn't even get into a liberal social pathology that I hope even chimps don't have. I'm referring to a common liberal pattern to punish the helpless innocent. A commits a crime. B gets punished.

Affirmation action is like that. In the 1950s and earlier, Democrat party politicians ran a legal system that kept black people out of many schools and colleges. Have we punished them? Hardly. Some are only now leaving politics at advanced ages. No, through affirmation action we only punish whites who weren't even alive when those violations occurred, in many cases these are people whose parents and grandparents never went to college. They never benefitted from the Democratic party's racist policies. Punish the innocent. Don't punish the guilty. That's liberalism.

Or take one that's been in the news recently, rape accompanied by pregnancy. Liberals would have us kill the baby, clearly an innocent and helpless bystander. Yet they surround the rapists with all sorts of publicity barriers and legal technicalities that will allow at least wealthy, well-connected rapists (think Bill Clinton) from even doing prison time.

Are liberals a throwback to our chimpist past? Maybe. But that all depends on what you believe about evolution.

Since Kate Shaw is studying "evolutionary biology and behavior," I'd be interested in her views on the topic.

Isn't the conclusion too premature? Just because this experiment did not observe third-party punishment, does not mean that it doesn't exist/occur in nature.

My biggest objection is that not all humans engage in third-party punishment either. In fact, only a minority do- only the leaders (government) typically punish criminals. I think the chimp given the chance to be third-party punisher would most likely do it if it was an alpha male with some stewardship of the victim or at least some interest/friendship/bond with the victim.

Do this experiment with three human strangers, and I'm sure third-party punishment will not be observed either.

Good points. If someone is robbed at gunpoint I'm not going to go up to the robber and try to return the stolen goods. Wouldn't the punisher chimp risk retribution later, for no obvious benefit to himself (unless he's an alpha)?

Everyone's focusing on third-party punishment in a criminal transgression setting, but this can be much smaller than that. Picture a group of people hanging out, and one of them says something mean or nasty to another. If the group thinks that comment was unwarranted, the speaker is likely to be reined in by the group, or ejected entirely.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

But in human society, not everybody would assume the role of group C, I know I wouldn't in most cases. Unless the person that gets hurt is someone I care for or some other impulses push me to interfere like an adult hitting a child, I wouldn't interfere.

So like the other, I don't find this experiment very conclusive. Like someone said, what if the punisher was the mother of the victim? Would the mom chimp have interfered in favor of her kid more than to any random chimp?

If I see some acts on the street, I might hide and call the cops, but chances I interfere myself are low!

Just came here to say this. Furthermore, Chimps are known to generally use violence to get things done while Bonobos seem to use more social means. It would be very interesting to repeat this experiment with Bonobos.

Isn't the conclusion too premature? Just because this experiment did not observe third-party punishment, does not mean that it doesn't exist/occur in nature.

My biggest objection is that not all humans engage in third-party punishment either. In fact, only a minority do- only the leaders (government) typically punish criminals. I think the chimp given the chance to be third-party punisher would most likely do it if it was an alpha male with some stewardship of the victim or at least some interest/friendship/bond with the victim.

Do this experiment with three human strangers, and I'm sure third-party punishment will not be observed either.

Humans spend an incredible amount of time in third party punishment. Nearly every time people gossip and say so and so is mean or cheap, tell our kids to have good manners, or otherwise criticize those around us we are engaging in third party punishment. We just normally use social coercion as our preferred method and like to gather groups of people to assist. That is on top of the time spent on actual laws and such. Animals may have more complex societies than humans realize, but humans society really is a whole magnitude more complex than anything else we know of.

Also, though we don't do it with a tray of food with adults, humans do normally show third party punishment in experiments. When you give a person the opportunity to enforce a fair decision in an experiment, they normally take it.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

She doesn't miss the point at all. That these studies need to be on chimps in the wild via observation was my first thought as well, because the lab environment cannot duplicate or control for a potentially vast number of influences, such as hierarchy, role, scarcity or resources, etc, in combination. The chimps in the lab my also not fully understand the intent of the feeding and may not view theft in this case as undesirable. It's a study that is absolutely crappy at face value.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

No third-party punishments among chimps? Then what they've found is that monkeys are a lot like soft-on-crime liberals. Liberals have little interest in punishing crimes that don't impact them personally. They'd rather spend money on 'root causes,' which are invariably liberal causes.

That doesn't even get into a liberal social pathology that I hope even chimps don't have. I'm referring to a common liberal pattern to punish the helpless innocent. A commits a crime. B gets punished.

Affirmation action is like that. In the 1950s and earlier, Democrat party politicians ran a legal system that kept black people out of many schools and colleges. Have we punished them? Hardly. Some are only now leaving politics at advanced ages. No, through affirmation action we only punish whites who weren't even alive when those violations occurred, in many cases these are people whose parents and grandparents never went to college. They never benefitted from the Democratic party's racist policies. Punish the innocent. Don't punish the guilty. That's liberalism.

Or take one that's been in the news recently, rape accompanied by pregnancy. Liberals would have us kill the baby, clearly an innocent and helpless bystander. Yet they surround the rapists with all sorts of publicity barriers and legal technicalities that will allow at least wealthy, well-connected rapists (think Bill Clinton) from even doing prison time.

Are liberals a throwback to our chimpist past? Maybe. But that all depends on what you believe about evolution.

Since Kate Shaw is studying "evolutionary biology and behavior," I'd be interested in her views on the topic.

--Michael W. Perry, editor of Eugenics and Other Evils

Does anyone know where I can find the "failed troll is a failure" graphic?

I have observed this absence of "third-party punishment" in (at least some) humans as well, so chimps aren't entirely the odd man out here. More than once in my life I've been in situations where I was the agent trying to enforce this third-party punishment - standing up for someone else being wronged - and had the perpetrator confront me directly and ask, "Why are you all in my face about this when I'm not doing it to you?"

Seriously, we need to keep in mind that there's a very real spectrum here, and some "humans" are scarcely more capable than chimpanzees in this and other cognitive aspects. It's likely some lucky chimps actually fall within the human range of the spectrum for some cognitive functions. Look out, Caesar is coming to save the apes!

Everyone's focusing on third-party punishment in a criminal transgression setting, but this can be much smaller than that. Picture a group of people hanging out, and one of them says something mean or nasty to another. If the group thinks that comment was unwarranted, the speaker is likely to be reined in by the group, or ejected entirely.

Depends on the size of the group and the social dynamic of the setting. But you're right, doesn't have to be criminal.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

But in human society, not everybody would assume the role of group C, I know I wouldn't in most cases. Unless the person that gets hurt is someone I care for or some other impulses push me to interfere like an adult hitting a child, I wouldn't interfere.

So like the other, I don't find this experiment very conclusive. Like someone said, what if the punisher was the mother of the victim? Would the mom chimp have interfered in favor of her kid more than to any random chimp?

If I see some acts on the street, I might hide and call the cops, but chances I interfere myself are low!

I think you're underestimating the human desire to enforce justice. Also note that the barrier/risk for the punisher is non-existent. All the chimp has to do is push a button and the thief gets no banana. It's not like the example of the bully where you put yourself at risk to enforce justice. I suspect and the article implies that the chimps did push the button. So they weren't afraid too. So I think it's fair to say that if this test evoked even a small sense of justice it would have presented in the results. Although I agree that it's worth questioning how well constructed this study was. I just don't think your criticism of "maybe they just didn't want to interfere" is applicable. I have no doubt that humans in a similar study would pass every time.

I have observed this absence of "third-party punishment" in (at least some) humans as well, so chimps aren't entirely the odd man out here. More than once in my life I've been in situations where I was the agent trying to enforce this third-party punishment - standing up for someone else being wronged - and had the perpetrator confront me directly and ask, "Why are you all in my face about this when I'm not doing it to you?"

Seriously, we need to keep in mind that there's a very real spectrum here, and some "humans" are scarcely more capable than chimpanzees in this and other cognitive aspects. It's likely some lucky chimps actually fall within the human range of the spectrum for some cognitive functions. Look out, Caesar is coming to save the apes!

LOL, look on the bright side. Instead of asking why you were in their face, they could have just started flinging poo.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

I don't see this with humans very often without there being some other factor involved. This test isn't social, none know each other nor have a group dynamic. The whole notion that this doesn't happen because we don't see it in this experiment is a flawed thought because there is lots of evidence of alphas in nature that control groups of chimps and punishments get meted out. This experiment gives no insights, what they are asking for is something asocial - has no social context. There is no win for the interfering chimp only negative consequences for taking away someones food.

How would you ascribe a positive result? That chimps would take away others food without any benefit to either the questionably "harmed" party nor the interring party, that would only harm the other chimp by taking away his food. This just seems like a very poor experiment to answer the question, and to come to any conclusion seems not very thoughtful.

I think you're underestimating the human desire to enforce justice. Also note that the barrier/risk for the punisher is non-existent. All the chimp has to do is push a button and the thief gets no banana. It's not like the example of the bully where you put yourself at risk to enforce justice. I suspect and the article implies that the chimps did push the button. So they weren't afraid too. So I think it's fair to say that if this test evoked even a small sense of justice it would have presented in the results. Although I agree that it's worth questioning how well constructed this study was. I just don't think your criticism of "maybe they just didn't want to interfere" is applicable. I have no doubt that humans in a similar study would pass every time.

I don't think you can draw inferences from the existence of the cage. It is unlikely that steel cages are factored into chimps instinctual behaviors "I will do x, unless separated by a steel cage". We know from the experiment, for example, that socially inferior chimps are much less likely to punish a dominant chimp in the direct-punishment scenarios, even though by your logic the existence of the cage should allow an inferior to punish a superior with impunity.

I also believe you are overestimating the human desire to directly enforce justice. Humans like to see justice done. Humans tend to not be big fans of being the ones doing the justice.

Imagine you're hanging out with a large group of friends. A couple of your friends say something mean to one of your other friends. The group will most likely step in in some way.

However, now imagine you are hanging out with just two other friends. One of them says something mean to the other. Do you do anything? I think very often the answer is that a human in that situation may think about doing something, but in the end will decline to step in.

Now think back to the former example where there's a group. When the group does decide to step in, there is often a short pause while the group waits to see what everyone else will do. Then someone will say something, and everyone else will jump in to support. It tends to be a group dynamic, with individuals wary of taking a lone stand.

My original field was evolutionary animal behavior. I mention that because it involves my criticism of the experiments. People will exhibit the same behavior in prisons. They will also often exhibit the same behavior in small social settings. After all animals, and people, don't always behave the same in different groupings.

This is work that really needs to be done in the field, with a natural group of animals. Only long term observation will really tell us what they do under these circumstances. We do know that chimps do exhibit altruistic behavior under a number of different situations involving third parties. This experiment seems to ignore those long term findings.

Kate, I would think that your own experiences would show that.

What my experiences show me that it is nearly impossible to collect observational data that is meaningful and reliable when it comes to such a complicated and subtle behavior.

I agree that because of the laboratory setting, the experiment is not entirely conclusive, and perhaps I should have mentioned that in the write-up. However, I don't believe that either experimental trials in the wild or purely observational studies of free-living animals can evaluate this behavior with the same kind of nuance and control that this study does.

There are too many factors that can limit the reliability of the results. What is the motivational state of the animals at the time? What has happened just before the trial that might affect the results? Is the thief stealing something of relatively similar value in each situation? How many other chimpanzees are present, and who are they? Can we be sure that the potential punisher even saw the aggression? These are just a few factors that can be controlled for in a laboratory setting, and could either cloud or obscure any findings in a study in the wild.

Although this experiment cannot conclusively say that there is no situation in which chimpanzees exhibit third-party punishment, the use of second-party punishment suggests that the task was not entirely foreign to the chimpanzees, and it is surprising and interesting that there was no evidence of unaffected individuals punishing transgressors. The study isn't perfect, and it probably raises more questions than it answers, but I certainly think it's valid.

I have observed this absence of "third-party punishment" in (at least some) humans as well, so chimps aren't entirely the odd man out here. More than once in my life I've been in situations where I was the agent trying to enforce this third-party punishment - standing up for someone else being wronged - and had the perpetrator confront me directly and ask, "Why are you all in my face about this when I'm not doing it to you?"

Seriously, we need to keep in mind that there's a very real spectrum here, and some "humans" are scarcely more capable than chimpanzees in this and other cognitive aspects. It's likely some lucky chimps actually fall within the human range of the spectrum for some cognitive functions. Look out, Caesar is coming to save the apes!

LOL, look on the bright side. Instead of asking why you were in their face, they could have just started flinging poo.

Don't laugh... I was in a situation once that resulted in a deranged guy coming back and flinging some creature's poo at a store window. I think he's in a zoo somewhere now, flinging poo at visitors.

I keep thining about what the result would be in humans. I would love to see Dan Ariely or one of the other behavioral economics guys do this experiment. I suspect that if you did the same setup, but used small sums of money, you wouldn't see a very large effect (but you might see some signal).

Imagine a few college students asked to participate in a psychology experiment. Let's not prejudge with labels, so let's just call the participants A, B and C. Get everyone in the same room. The experimenter hands A an amount of money, say $5, for essentially no reason. B has the option of taking the $5 away from A. If B takes the money, then the experimenter asks C if B should be able to keep the money. If C makes B give up the $5, he gets no benefit except for perhaps a feeling of justice.

If you were C, would you really care? Would you even think of that as stealing? Remember, A did nothing to earn the money in the first place. Participant A may feel like B stole from him, and want him punished. But is that how C would perceive what just happened?

Which raises another possibility for how to tweak the experiment for chimps. What if the "victim" clearly had worked hard for the food, rather than being randomly given some food by the researchers?

EDIT: Said another way: In the experiment, one chimp sees a conflict between two other chimps over food. Neither one of the two that are in conflict had to work particularly hard to get the food. Which chimp had the food first may simply be irrelevant to the way a third-party chimp views the conflict. It may only be relevant to the two chimps involved.

EDIT 2: Another way of thinking about it: You're walking down the street. You see a guy reach down and start to pick up a $5 bill lying on the ground. At the last second, the bill blows away and another guy picks it up instead. Do you step in to try to get justice for the first guy?

My original field was evolutionary animal behavior. I mention that because it involves my criticism of the experiments. People will exhibit the same behavior in prisons. They will also often exhibit the same behavior in small social settings. After all animals, and people, don't always behave the same in different groupings.

This is work that really needs to be done in the field, with a natural group of animals. Only long term observation will really tell us what they do under these circumstances. We do know that chimps do exhibit altruistic behavior under a number of different situations involving third parties. This experiment seems to ignore those long term findings.

Kate, I would think that your own experiences would show that.

What my experiences show me that it is nearly impossible to collect observational data that is meaningful and reliable when it comes to such a complicated and subtle behavior.

I agree that because of the laboratory setting, the experiment is not entirely conclusive, and perhaps I should have mentioned that in the write-up. However, I don't believe that either experimental trials in the wild or purely observational studies of free-living animals can evaluate this behavior with the same kind of nuance and control that this study does.

There are too many factors that can limit the reliability of the results. What is the motivational state of the animals at the time? What has happened just before the trial that might affect the results? Is the thief stealing something of relatively similar value in each situation? How many other chimpanzees are present, and who are they? Can we be sure that the potential punisher even saw the aggression? These are just a few factors that can be controlled for in a laboratory setting, and could either cloud or obscure any findings in a study in the wild.

Although this experiment cannot conclusively say that there is no situation in which chimpanzees exhibit third-party punishment, the use of second-party punishment suggests that the task was not entirely foreign to the chimpanzees, and it is surprising and interesting that there was no evidence of unaffected individuals punishing transgressors. The study isn't perfect, and it probably raises more questions than it answers, but I certainly think it's valid.

No the problem is exactly the reverse. There are so many factors that it cannot be controlled for properly in the lab. In the wild, it suffices to observe third-party justice a statistically significant number of times, after interpretation, and you're good to go. Another advantage is that you have a large sample size of chimps under observation. Suppose, hypothetically, that chimps defer third party-justice to those they see as dominant in the lab, which might at times be the human caretakers, and thus you will never find a situation in the lab where chimps mete out justice. I hesitate to give this hypothetical example because you might focus on it instead of any of thousands of combinations of factors that can artificially limit chimp behavior.

My original field was evolutionary animal behavior. I mention that because it involves my criticism of the experiments. People will exhibit the same behavior in prisons. They will also often exhibit the same behavior in small social settings. After all animals, and people, don't always behave the same in different groupings.

This is work that really needs to be done in the field, with a natural group of animals. Only long term observation will really tell us what they do under these circumstances. We do know that chimps do exhibit altruistic behavior under a number of different situations involving third parties. This experiment seems to ignore those long term findings.

Kate, I would think that your own experiences would show that.

What my experiences show me that it is nearly impossible to collect observational data that is meaningful and reliable when it comes to such a complicated and subtle behavior.

I agree that because of the laboratory setting, the experiment is not entirely conclusive, and perhaps I should have mentioned that in the write-up. However, I don't believe that either experimental trials in the wild or purely observational studies of free-living animals can evaluate this behavior with the same kind of nuance and control that this study does.

There are too many factors that can limit the reliability of the results. What is the motivational state of the animals at the time? What has happened just before the trial that might affect the results? Is the thief stealing something of relatively similar value in each situation? How many other chimpanzees are present, and who are they? Can we be sure that the potential punisher even saw the aggression? These are just a few factors that can be controlled for in a laboratory setting, and could either cloud or obscure any findings in a study in the wild.

Although this experiment cannot conclusively say that there is no situation in which chimpanzees exhibit third-party punishment, the use of second-party punishment suggests that the task was not entirely foreign to the chimpanzees, and it is surprising and interesting that there was no evidence of unaffected individuals punishing transgressors. The study isn't perfect, and it probably raises more questions than it answers, but I certainly think it's valid.

Hi Kate,

Don't mean to disrespect your work, but if I was thinking of how to make an experiment on how this would work on Chimpanzees, I would first think of how this would be for school kids. How would you make an experiment to test this on school kids. We as adult humans live in a very large and complex society, we see big pictures about laws under large groups. Both chimps and children do not have these big picture ideals as they live in small groups, not sure projecting big picture expectations on a small group will likely yield the proper results.

Might be able to check with a group of kids if this behaviour is typical, then check with a group of chimps. Some ideas.

There are some insightful posts here. I don't know a lot about these particular primates. However, it may be possible that the one usually responsible for dishing out punishment is the leader - or possibly one of the grey backs. If this is the case, it may make perfect sense why the third character did not intervene - as they didn't see themselves as the leader. From the reading, I wasn't able to determine the permutations tested or the criteria for each of the candidates for this trial.

I'm inclined to think this trial is inconclusive. The environment is wrong and there are no group dynamics involved. Group dynamics have a significant impact on behaviour.

Seems an odd experiment to ascertain this. You are harming one without compensating the other, it would not be socially beneficial for either to do this. If it gave back the banana than you might have something, but without appreciable "making a difference" there is little value to the interfering monkey other than annoying the other monkey and make him pissed off at the interfering monkey.

What they are asking for is asocial behaviour, doing it from their own judgement.

It's kind of like bullies in school, what make kids interfere with a bully? Sure they see it as unfair, but unless they have a dog in the fight (a friend) or somehow can make an appreciable difference they aren't going to interfere, interference is just going to get the attention of the bully.

You entirely missed the point of the study. In human society person A hurts person B and group C (prosecutors, judge, jury) punish person A for no other reason than to enforce justice. The point is to see whether chimp society has this mechanism as well. Of course it doesn't happen all the time for the reasons you point out but humans are capable of it, and no other animals are as far as we know.

I definitely wonder whether this scenario is just too abnormal to evoke this behavior. As the article points out Chimps and other primates exhibit most components of human society that we try to analyze them for and I'm a bit surprised to see this one missing.

But in human society, not everybody would assume the role of group C, I know I wouldn't in most cases. Unless the person that gets hurt is someone I care for or some other impulses push me to interfere like an adult hitting a child, I wouldn't interfere.

So like the other, I don't find this experiment very conclusive. Like someone said, what if the punisher was the mother of the victim? Would the mom chimp have interfered in favor of her kid more than to any random chimp?

If I see some acts on the street, I might hide and call the cops, but chances I interfere myself are low!

Also, the other important aspect is the cost of interference or cost of enforcement ... the law enforcement or judicial examples folks are using have a big caveat - it is their job that they are paid to do. Therefore, there is monetary motivation to do it. The real question is; with no positive motivation (monetary or otherwise), would a human willingly assume the role of punishment/enforcement? In a circular manner, it may even be argued that those who are willing to accept such a role without monetary motivation are possible gaining something intangible through the punisher/punishee interaction.

In other words, I am wondering if a truly ideal case of "completely dispassionate/disinterested enforcer of justice" exists - either in human society or in animal society. Can someone more knowledgeable in these areas help me understand this?

In other words, I am wondering if a truly ideal case of "completely dispassionate/disinterested enforcer of justice" exists - either in human society or in animal society. Can someone more knowledgeable in these areas help me understand this?

There is not a "completely dispassionate/disinterested enforcer of justice". But that's not what this topic is all about, anyway. The question is not whether the enforcer is a perfect enforcer. The question is whether members of the species even try to be imperfect enforcers.

The original prototype for the third-party punisher in human societies would probably the patriarch of a small clan. His incentive (evolutionarily speaking, that is) is not necessarily to mete out perfect justice. His incentive is to minimize intra-group conflict. "I don't care who started it", might often be the most efficient response from that perspective. The trick is, though, that it can't always be the response.

Evolutionarily, justice doesn't have to be perfect. It just has to be better than nothing.

Kate Shaw Yoshida / Kate is a science writer for Ars Technica. She recently earned a dual Ph.D. in Zoology and Ecology, Evolutionary Biology and Behavior from Michigan State University, studying the social behavior of wild spotted hyenas.